The present invention relates to medical bandaging and, in particular, to an improved stretchable woven or nonwoven polymer wound closure strip exhibiting a high degree of dynamic adhesion.
Wounds closure strips, along with staples and various other mechanical fasteners have recently become acceptable alternatives for sewn stitches in closing many types of skin wounds. Wound closure adhesive bandages are in many respects more desirable than stitches in that they facilitate wound healing by adhesively binding the underlying portions of the wound in direct contact with a flush skin surface, Hence, upon healing, scar tissue is minimized, especially scar tissue that would otherwise show the stitch marks and/or closure line.
While wound closure strips may take various forms and be fabricated in a variety of shapes, they typically comprise a sterile piece of adhesive backed tape of a suitable length that upon mounting over the wound, acts to hold the exposed wound closed. One commonly known and pre-existing form of this bandaging comprises a butterfly bandage wherein the bandage is configured in the general shape of a butterfly. That is, it has a pair of relatively large surface area adhesive portions connected by a relatively narrow section (much like the shape of an hour glass or butterfly) and which narrow portion is placed over a closed wound, while the larger portions maintain the wound surfaces in contact.
Typically, the material previously employed in such bandaging has included a plurality of lengthwise fiberglass strands supported in a paper-like carrier or backing. The strands provide rigidity to the bandaging. Such tape and fiber glass strands are also configured to "breathe". A drawback to the use of fiberglass strands in the paper-like tape, however, has been that the bandaging is not permitted to move or stretch along the direction of the fiberglass strands as pressure is placed on the wound by the patient during normal activities. Thus, with normal movement, the wound closure strip on opposite sides of the wound tend to stretch the skin with resulting mechanical damage to the skin at the extreme ends of the bandage or release of the wound closure strip from the skin. Further, when left in place for some time, the backing material deteriorates and upon removing such wound closure strips, the individual fiberglass strands do not lift as a unit from the skin, and oftentimes it is required that a medical attendant separately pick each strand of fiber from the skin using forceps, upon removal of the wound closure strip.
It is with the foregoing problems in mind that the present invention was designed and developed as an improvement to permit the stretching of the wound closure strip with the skin movement and to prevent the leaving of a bandage residue, upon wound closure strip removal. The wound closure strip must exhibit a porosity great enough to allow for a movement of exudates through the strip without causing release of the wound closure strip from the skin. Specifically, these ends are achieved in the present invention via the fabrication of the present wound closure strips from a woven or non-woven, polymer based material which is designed to exhibit a stress, strain modulus compatible with that of the underlying skin. Since the intent is to produce a thin closure relative to its width for optimum flexibility and this goal is to be a function of the planar stretch characteristic of the underlying skin, this property can be defined as follows: ##EQU1## where stress is defined as the load divided by the unit width, and strain is defined as the change in unit length divided by the gauge length. More particularly, it is desired to have a modulus higher than, or at least equal to, that of the underlying skin to provide some reinforcement to the skin and to allow for the fact that the closure strips cover only a part of the wound length. If the modulus, E.sub.t, is expressed in pounds per inch, a useful range as far as the application to wound closure strips is concerned has been found to be from 0.5 to 110.
The material is further fabricated to permit the bandage to breathe and the material is such that upon bandage removal, it does not separate to leave undesired residue. When forming the present wound closure strip, this material is cut at a predetermined bias angle to provide the desired modulus, E.sub.t. This provides the individual strips with a property of "dynamic adherence" that permits the bandage to stretch along with the skin, thereby reducing mechanical damage to the skin or release of the wound closure strip from the skin during movement or swelling of the skin.
A further embodiment of the invention involves the degree of permanence of the elastic properties of the bandage material. It is fairly obvious that a very high modulus bandage material can cause skin damage and wound closure release because of its unyielding nature. It is no less true, however, that a low modulus material with good elastic recovery can also cause a degree of the same distress depending upon the extent of the application pre-load. It would be inconvenient to require the medical practitioner to limit the extent of the load he or she applies to the bandage strip when mounting it over the wound. It is, therefore, important that the wound closure material not only have low elastic modulus, but also poor elastic recovery. Thus, a material with a stress, strain modulus within the above desired range would be unacceptable if it also possessed an elastic recovery equal to or above the range of commercially available urethane film bandages such as the Smith Nephew Company's Opsite.TM., the 3 M Company's Tegaderm.TM. and Johnson & Johnson's Bioclusive.TM..
A bandage material elastic modulus, E.sub.t, compatible with that of human skin provides required support over the wound area. The stress relaxation characteristic or poor elastic recovery provides a comfortable complianace during the period of healing. Together, these properties provide "dynamic adherence" of the wound closure strip.
The above objects, advantages and distinctions of the present invention will become more apparent, however, upon reference to the following description and to the appended drawings. Before referring thereto, though, it is to be recognized that the following description is made with respect to the presently preferred embodiment only and that various modifications may be made thereto such as in the ultimate shape of the bandage, its stress/strain modulus, etc.